This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A047348 #32 Sep 24 2022 08:16:31
%S A047348 2,4,9,11,16,18,23,25,30,32,37,39,44,46,51,53,58,60,65,67,72,74,79,81,
%T A047348 86,88,93,95,100,102,107,109,114,116,121,123,128,130,135,137,142,144,
%U A047348 149,151,156,158,163,165,170
%N A047348 Numbers that are congruent to {2, 4} mod 7.
%C A047348 Also, integer values of (n*(n+1)+1)/7. - _Bruno Berselli_, Jan 25 2013
%H A047348 David Lovler, <a href="/A047348/b047348.txt">Table of n, a(n) for n = 1..1000</a>
%H A047348 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).
%F A047348 From _R. J. Mathar_, Dec 16 2009: (Start)
%F A047348 a(n) = a(n-1) + a(n-2) - a(n-3).
%F A047348 G.f.: x*(2+2*x+3*x^2)/((1+x)*(x-1)^2). (End)
%F A047348 a(n) = 7*floor((n-1)/2) + 3 + (-1)^n. - _Gary Detlefs_, Mar 02 2010
%F A047348 a(n) = 7*n - a(n-1) - 8 with n > 1, a(1)=2. - _Vincenzo Librandi_, Aug 05 2010
%F A047348 E.g.f.: 3 + ((14*x - 9)*exp(x) - 3*exp(-x))/4. - _David Lovler_, Sep 12 2022
%p A047348 seq(7*floor((n-1)/2)+3 +(-1)^n,n=1..49); # _Gary Detlefs_, Mar 02 2010
%t A047348 LinearRecurrence[{1,1,-1},{2,4,9},50] (* _Harvey P. Dale_, Aug 04 2016 *)
%o A047348 (PARI) a(n) = (14*n - 9 - 3*(-1)^n)/4 \\ _David Lovler_, Sep 18 2022
%K A047348 nonn,easy
%O A047348 1,1
%A A047348 _N. J. A. Sloane_